Submerged clamp bar

ABSTRACT

In a palletizing device including a layer formation structure defining a layer building plane, a contact element moves between a first position an a second position, said first position being at least one of at and below said layer building plane and said second position being above said layer building plane

RELATED APPLICATIONS

[0001] The present invention is a continuation-in-part of co-pendingU.S. patent application Ser. No. 09/920,317 entitled SynchronizedPalletizer and filed Aug. 1, 2001.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to article manipulationdevices and particularly to a palletizing device and method ofoperation.

[0003] Palletizers receive a sequence of items and produce a palletizedstack of items. Generally, items are formed into rows, rows formed intolayers, and layers stacked upon a pallet to form a palletized stack ofitems. Thus, a typical palletizer receives a series of items andorganizes the items by row, by layer, and ultimately as a palletizedstack of items on a pallet.

[0004] Palletizing calls for efficiency. In many applications, time ismost critical. A palletizer more efficiently, i.e., more quickly,organizing an incoming series of items into a palletized stack of itemsrepresents advantage in greater production levels, i.e., greater itemthroughput.

[0005] Another important palletizing consideration is size. A morecompact machine takes less floor space and, if necessary, accommodatesmore palletizing machines in the same area as would be occupied byrelatively larger palletizing machines. Compact size is, therefore, adesirable feature in a palletizer.

[0006] Accordingly, it would be desirable to provide a palletizer havingboth improved time efficiency and reduced overall size relative toconventional palletizing devices. The subject matter of the presentinvention provides such a palletizer.

SUMMARY OF THE INVENTION

[0007] In a palletizing device including a layer formation structuredefining a layer building plane, a contact element moves between a firstposition an a second position, said first position being at least one ofat and below said layer building plane and said second position beingabove said layer building plane

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the invention, and to show how thesame may be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings in which:

[0009]FIG. 1 illustrates in perspective a synchronized palletizer.

[0010]FIG. 2 illustrates in plan view the synchronized palletizer ofFIG. 1 as taken along lines 2-2 of FIG. 1.

[0011]FIG. 3 illustrates in side view a layer head of the palletizer ofFIG. 1.

[0012]FIG. 4 illustrates in perspective the layer head of FIG. 3.

[0013]FIG. 5 illustrates in perspective a dead plate of the layer headof FIGS. 3 and 4.

[0014]FIG. 6 illustrates separately a submerged bar clamp operating asan alternative to the dead plate of FIGS. 3-5.

[0015]FIGS. 7-10 illustrate the submerged bar clamp of FIG. 6 asintegrated into a layer head.

[0016]FIGS. 11-16 illustrate schematically operation of a layer head andthe submerged bar clamp of FIGS. 6-10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017]FIG. 1 illustrates in perspective and FIG. 2 in side view apalletizer 10. In FIGS. 1 and 2, palletizer 10 includes a frame 12 ofgenerally box-form configuration. Frame 12 includes four vertical posts,individually posts 12 a-12 d, supporting an upper structure comprisinghorizontal beams 12 e-12 h. Thus, the lower end of each of posts 12 a-12d rests on a floor and the upper ends of posts 12 a-12 d support beams12 e-12 h. Beams 12 e-12 h provide a generally horizontal rectangularstructure maintained at a given level above floor level. Generally,frame 12 provides a relatively compact overall structure supportingtherein elements of palletizer 10 as described more fully hereafter.

[0018] Adjacent frame 12, palletizer 10 includes an infeed conveyor 14.Infeed conveyor 14 is a “production level” conveyor receiving, forexample, output from a production or manufacturing operation or from arepackaging operation. Infeed conveyor 14 includes along its length aseries of live, i.e., powered, rollers 14 a. Infeed conveyor 14 alsoincludes a case turner 16. Case turner 16 manipulates incoming items 18,e.g., cases of products, appropriately according to programmed layerbuilding patterns. Use of case turner 16 and layer building methods andpatterns are well known in the art.

[0019] Generally, infeed conveyor 14 moves a series of items 18therealong for presentation to the remaining portions of palletizer 10as operating within frame 12. As may be appreciated, infeed conveyor 14and turner 16 operate cooperatively to appropriately orient a sequenceof items 18 according to a programmed layer building pattern includingcontemplation of necessary sequential row patterns interfitting to formlayer patterns and layer patterns interrelating to produce a stablestack of items on a pallet 40. Thus, it will be understood that items 18are not necessarily symmetrical and may be oriented according to aspecific predefined layer building pattern taking into accountrow-by-row variations within a layer and layer-to-layer variations foradjacent layers on a stack of item 18 layers resting on pallet 40.

[0020] Within frame 12, palletizer 10 includes a verticallyreciprocating row conveyor 20 and a vertically reciprocating layer head22. A row conveyor lift motor 24 when actuated vertically reciprocatesconveyor 20 as indicated at reference numeral 21. A layer head motor 26when actuated vertically reciprocates layer head 22 as indicated atreference numeral 23. Generally, each of row conveyor 20 and layer head22 are independently suspended within frame 12. More particularly, rowconveyor 20 hangs from four suspension points 25. Layer head 22 hangsfrom four suspension points 27. Each of conveyor 20 and layer head 22carry a pair of guides 29. Each of vertical posts 12 a-12 d carry ontheir inner surface a corresponding guide track 31. Thus, guide tracks31 on posts 12 a and 12 d interfit guides 25 of row conveyor 20 andmaintain conveyor 20 along a vertical path within frame 12. Similarly,guide tracks 31 on vertical posts 12 b and 12 c interfit with guides 27on layer head 22 to maintain layer head 22 along a vertical path withinframe 12.

[0021] Suspension chains and associated sprockets couple each of rowconveyor 20 and layer head 20 to the respective motors 24 and 26. Moreparticularly, row conveyor 20 hangs within frame 20 from a first set offour suspension chains 32 routed through appropriate sprockets 34 andcoupled to motor 24. Actuation of motor 24 in a first direction lowersrow conveyor 20 and actuation in the opposite direction raises rowconveyor 20. Specifically, the output shaft 24 a of drive motor 24extends the length of horizontal beam 12 e (shown only partially inFIG. 1) and carries at each end a pair of sprockets 34 a. Suspensionchains 36 engage sprockets 34 a and move in response to rotation ofsprockets 34 a. One end of each of chains 32 couples to a suspensionpoint 25 and the other end of each of suspension chains 32 carries acounter weight (not shown) depending directly below each pair ofsprockets 34 a. In this manner, chains 32 remain engaged relative tosprockets 34 a and, therefore, relative to drive motor 24.

[0022] Similarly, a second set of four suspension chains 36 andsprockets 38 suspend layer head 22 within frame 12 and couple to motor26. Actuation of motor 26 in a first direction moves layer head 22upward and actuation in the opposite direction lowers layer head 22.Specifically, the output shaft 26 a of drive motor 26 extends the lengthof horizontal beam 12 g (shown only partially in FIG. 1) and carries ateach end a pair of sprockets 38 a. Suspension chains 36 engage sprockets38 a and move in response to rotation of sprockets 38 a. One end of eachof chains 36 couples to a suspension point 27 and the other end of eachof suspension chains 36 carries a counter weight (not shown) dependingdirectly below each pair of sprockets 38 a. In this manner, chains 36remain engaged relative to sprockets 38 a and, therefore, relative todrive motor 26.

[0023] Thus, row conveyor 20 and layer head 22 operate independently andmay be vertically positioned by appropriately actuating and controllingmotors 24 and 26, respectively.

[0024] Row conveyor 20 moves to a lower position vertically coincidentwith the height of infeed conveyor 14 to receive from infeed conveyor 14one or more rows of items 18. As discussed above, the items 18 presentedto row conveyor 20 at the output of conveyor 14 correspond to an ongoinglayer building pattern, i.e., particular ones of the items 18 within agiven row are suitably oriented according to and overall sequence ofitem 18 orientation pattern. As live rollers 14 a propel a sequence ofitems 18 onto row conveyor 20, live rollers 20 a activate and collectthe sequence of items 18 as a row or rows onto conveyor 20. As may beappreciated, live rollers 20 a are suitably operated in coordinationwith live rollers 14 a of conveyor 14 to pass serially a given set ofitems 18 from conveyor 14 onto conveyor 20. In this manner, conveyor 20receives items 18 from conveyor 14. Conveyor 20 is then verticallypositioned as necessary to vertically coincide with a current height oflayer head 22 to pass items 18 from conveyor 20 to layer head 22.

[0025] As may be appreciated, because both row conveyor 20 and layerhead 22 independently vertically reciprocate a broad combination ofrelative movements may be accomplished by programmed control to transferitems 18 from conveyor 20 to layer head 22, i.e., one of the two devicesmay be moved to match the height of the other or both moved to matchsome intermediate or predetermined height according to programmedcontrol. Generally, however, it is contemplated that the relativelyhigher speed conveyer 20 “chase” layer head 22, i.e., seek out a currentheight for layer head 22, when transferring items 18 from conveyor 20onto layer head 22. In this particular embodiment, conveyor 20 includesa row pusher 30 of generally conventional design including a pneumaticcylinder 30 a for pushing a row of items 18 from conveyor 20 onto layerhead 22. Thus, row conveyor 20 vertically aligns itself with a currentvertical position of layer head 22 and passes laterally items 18 fromconveyor 20 to layer head 22.

[0026] Generally, layer head 22 tracks the height of a stack of items 18layer as positioned on a pallet 40. Pallet 40 rests at floor level andreceives layer-by-layer items 18 from layer head 22. Once a completelayer of items 18 has been built on layer head 22, layer head 22deposits the entire layer as a next layer on pallet 40 or on a stack oflayers resting on pallet 40. As will be described more fully hereafter,layer head 22 withdraws its support from below a layer of items 18 anddrops the layer onto a pallet 40 below or onto a stack of item 18 layersresting on pallet 40 below. Layer head 22 then repositions itself, i.e.,raises, to prepare to receive a next item 18 layer from row conveyor 20.

[0027]FIGS. 3 and 4 detail layer head 22 as detached from frame 12. FIG.5 illustrates a dead plate 108 of layer head 22, but detached therefromfor purposes of illustration. In FIGS. 3-5, layer head 22 includes a setof free rollers 100 carried on a pair of chains 102 a and 102 b.Sprockets 103 a constrain chain 102 a to an L-shaped path. Similarly,sprockets 103 b restrict chain 102 b to a corresponding L-shaped path.Rollers 100 attach to a length segment of chain 102 a and thereby createa removable floor relative to layer head 22. A drive shaft 105 couplesto one of sprockets 103 a and one of sprockets 103 b and thereby tiestogether chains 102 a and 102 b. Drive motor 104 turns shaft 105 to movechains 102 a and 102 b along their respective and coordinated L-shapedpaths. A pair of vertical plates 110, individually 110 a and 110 b,support shaft 105 and also carry thereacross a stop 111, i.e., a raisededge formation. Stop 111 engages a leading lower edge of an item 18layer while being dropped from layer head 22.

[0028] Floor drive motor 104 operates to move chains 102 and therebywithdraw rollers 100 from a supporting or floor position relative to anitem 18 layer to an open position allowing an item 18 layer to dropthrough layer head 22 onto a pallet 40 therebelow or onto a stack ofitem 18 layers therebelow. Advancing rollers 100 rightward, in the viewof FIGS. 3 and 4, moves rollers 100 out of a floor position asillustrated in FIG. 4 and into an open position occupying the verticalportion of the L-shaped path provided by sprockets 103 and chains 102.Once the leading edge of the item 18 layer engages stop 111, the item 18layer holds its position and rollers 100 continue to move out fromthereunder to drop the item 18 layer therebelow. The first row of items18 to fall from layer head 22 is the row most distant from stop 111.Thus, the first-to-arrive row of items 18, i.e., the row first placed onlayer head 22 when constructing a layer, is the last row to fall fromlayer head 22 when releasing an item 18 layer. The last-to-arrive rowis, therefore, the first row dropped from layer head 22. In this manner,a complete item 18 layer drops through the opened floor of layer head22.

[0029] Layer head 22 includes conditioning mechanisms to better organizea given item 18 layer thereon prior to dropping the layer on a pallet 40or a stack of layers therebelow. As discussed above, palletizer 10accommodates an ongoing layer building pattern. Items 18 of varyingorientation must be organized into a layer. A relatively loose, i.e.,with space therebetween, initial organization of items 18 betterfacilitates layer building patterns. Thus, as initially organized onlayer head 22, items 18 are loosely packed but possess the requiredrelative orientations to form, when brought together, a desired andcompact overall item 18 configuration within a given layer. Generally,layer head 22 includes conditioning mechanisms to collapse togetheralong orthogonal dimensions a loosely packed item 18 layer into atightly packed item 18 layer.

[0030] A pair of side clamps 106, individually 106 a and 106 b, movelaterally inward in a first dimension and compress together an item 18layer in preparation for deposit on a stack of item 18 layerstherebelow. A pneumatic cylinder 106 c couples by way of scissormechanism 107 (shown partially at reference numeral 107 a in FIG. 4) tooperate clamps 106 a and 106 b in parallel, i.e., move laterally inwardin parallel and coordinated orientation. A dead plate 108 (shownseparately in FIG. 5) rotates about an axis 108 a, i.e. flips up intoand past a vertical position, to compress a layer of items in a seconddimension. Thus, operating side clamps 106 and pivoting dead plate 108compresses together, in first and second mutually orthogonal dimensions,a layer of items 18 prior to deposit on a surface therebelow.

[0031] Thus, the process of building a layer row-by-row on lift head 22results in some disorganization or loose fitting layers requiring, foroptimal stacking, that the layers be compressed together in twodimensions, i.e. squeezed inward by bars 106 and plate 108, to make acompact organized layer ready for stacking on a surface therebelow.

[0032] In fact, a palletizer which permits significant disorganizationin an item 18 layer while constructing such layer row-by-row promotesrapid construction of the layer. For example, certain layer buildingpatterns require an interfitting relationship between rows within alayer. When such interfitting is required, it is easier and faster toinitially form the layer as a loose organization of items 18 to betterfacilitate rows having items 18 interfitting with other rows.

[0033] Palletizer 10 facilitates such loose organization of a layer ofitems 18 during construction thereof at upward-facing side plates 109 aand 109 b. Generally, side plates 109 are upward facing, smooth surfacesadjacent the ends of rollers 100 on each side of layer head 22. Rollers100 are of sufficient length to support a tightly-packed item 18 layerthereon. Rollers 100 need not be any wider than necessary to support anitem 18 layer thereon by virtue of support at side plates 109 a and 109b. More particularly, a loosely fitting item 18 layer occupies morearea, i.e., requires a greater support surface, than a tight-fittingitem 18 layer. Side plates 109 a and 109 b support the outer edges of aloosely-fitting item 18 layer and thereby provide a greater area forsupporting an item 18 layer during construction. In other words, layerhead 22 tolerates significant disorganization among layers during layerformation and thereby facilitates rapid layer construction on layer head22.

[0034] Once the layer has been loosely organized on the upward facingsurfaces of layer head 22, i.e., on rollers 100 and side plates 109 aand 109 b, dead plate 108 and side clamps 106 operate to drive togetherand compress the loosely organized item 18 layer into a tightly fittingitem 18 layer resting entirely on rollers 100.

[0035] As best seen in FIG. 4, the length of dead plate 108 correspondsto the length of rollers 100. Dead plate 108 includes, at each end,notches 108 b and 108 c, respectively. When plate 108 pivots upward, asindicated at reference numeral 108 d in FIG. 5, notches 108 b and 108 cleave an open space therebelow to accommodate inward movement of clamps106, i.e., inward and past the ends of dead plate 108. With dead plate108 moved to its “clamping” position, i.e., pivoted inward to engage andcompress and item 18 layer resting on layer head 22, side clamps 106move inward and if necessary reach beyond the ends of rollers 100 tothereby compress together in coordination with dead plate 108 an entireitem 18 layer from a loosely organized item 18 layer into atightly-fitting item 18 layer. As may be appreciated stop 111 operatesin coordination with clamps 106 and dead plate 108 to compress togetheran item 18 layer resting upon layer head 22. More particularly, stop 111resists movement of an item 18 layer in response to dead plate 108pivoting into its clamping position.

[0036] In FIG. 5, a pivot shaft 108 g mounts rotatably to layer head 22and carries thereon dead plate 108. A pair of pneumatic cylinders 108 ecouple by way of corresponding levers 108 f to pivot shaft 108 g. Thus,actuation of cylinders 108 e causes movement of dead plate 108 between atransition position as shown in FIGS. 4 and 5 and a clamping position,i.e., pivoted inward as indicated at reference numeral 108 g.

[0037] Thus, dead plate 108, rollers 100, side plates 109, stop 111 andside clamps 106 cooperatively tolerate significantly loose organizationamong items 18 when forming an item 18 layer and compress together items18 in a tight fitting layer supported entirely on rollers 100.

[0038] Dead plate 108 provides a transition surface filling a gapbetween row conveyor 20 and layer head 22. Conventional dead plates,i.e., transition devices, are generally fixed in position. Dead plate100 goes beyond a transition function and provides a compressionfunction. The horizontal position of dead plate 108 provides, therefore,a transition surface function when item 18 rows are pushed onto layerhead 22. After the last-to-arrive row of items 18 is located on layerhead 22, dead plate 108 pivots up to compress and provide a secondarybackstop for proper layer construction. Plate 108 thereby provides anability to lower into a generally horizontal conventional dead plateposition for a net fit between a reciprocating layer head 22 andwhatever it mates with for receiving rows, e.g., a row conveyor 20.Pivoting dead plate 108 provides also a layer compression device whichoperates in opposition to stop 111 as provided across plates 110. Inother words, dead plate 108 can push a layer against the stop 111 andthereby squeeze or compress the layer between plate 108 and stop 111.

[0039] Dead plate 108 provides a particularly important advantage duringlayer release, i.e., when rollers 100 are pulled from under an item 18layer to drop the item 18 layer through layer head 22. As discussedabove, dead plate 108 pivots into clamping or compressing engagementrelative to an item 18 layer to better organize and make compact theitem 18 layer in preparation for stacking. Leaving dead plate 108 insuch engagement improves release of the first row of items droppedthrough layer head 22. More particularly, and especially with respect tosmaller dimensioned items 18, dead plate 108 maintains a given anddesired position for a row of items 18 when it remains in contact withthe row of items 18 as they fall from of rollers 100 and onto asupporting surface therebelow. By guiding this first-to-drop row ofitems 18, dead plate 108 serves an additional guiding function relativeto items 18 when releasing a row of items 18 from layer head 22. Thisfirst-to-drop row of items 18 then serves a similar guiding functionrelative to a next-to-drop row of items 18. Eventually, the last-to-droprow of items 18, i.e., those adjacent stop 111, fall through layer head22 and find their final resting position on pallet 40 or on a stack ofitem 18 layers resting on pallet 40.

[0040] Prior art roller floors pulling support from under a layer ofitems suffer from a “loose” row which becomes more troublesome fornarrower item 18 dimensions. In other words, the narrower item 18 is thegreater its tendency to rock out of position when falling from rollers100. In accordance with the present invention, however, dead plate 108guides the first-to-drop item 18 row into position and begins acascading series of supporting elements, i.e., each row is guided intoposition by the previous row and the first row is guided into positionby dead plate 108. In this manner, an item 18 layer compressed togetheron layer head 22 achieves a more stable and better compressed finalposition after dropping through layer head 22 as it finds its finalresting place on pallet 40 or on a stack of item 18 layers resting onpallet 40.

[0041] Compressive forces applied to an item 18 layer by virtue of theitem 18 layer being captured and compressed between dead plate 108 andstop 111 also eliminate a dependence on conventional and undesirablyvariable compressive forces supplied by roller floors. In systems usingonly free rollers pulled from under an item 18 layer, the compressiveforce, i.e., against a fixed stop, varies as the roller bearings becomemore free turning by the unweighting thereof as items 18 fall therefrom.For particularly heavy items 18 and particularly free turning rollers100, moving rollers 100 out of a supporting position does not generatesignificant compressive forces relative to a load, i.e., the load doesnot bear heavily against a fixed stop under such conditions. Under thepresent invention, however, dead plate 108 maintains static compressionrelative to an item 18 layer regardless of item 18 layer weight anddegree of free-turning characteristic of rollers 100. As a result, anitem 18 layer dropped through layer head 22 enjoys a more compact andbetter organized final resting place on pallet 40 or on a stack of item18 layers resting on pallet 40.

[0042] Side plates 109 enhance use of rollers as a floor for a layerconveyor. The span occupied by rollers 100, i.e., as supported at eachend thereof at chains 102, is limited by the strength and deflectioncharacteristics of rollers 100. As may be appreciated, minimizing thelength of rollers 100 to occupy just sufficient distance to support anentire item 18 layer minimizes the cost and structural requirements ofrollers 100. Side plates 109 tolerate loose organization within an item18 layer during construction thereof. In conventional practice, a fortyinch wide finished width for a given item 18 layer requires a rollerfloor of over fifty inches wide to accommodate the layer duringconstruction. Under the present invention, however, rollers 100 needonly be forty inches wide because side plates 109 support the outeredges of a layer during construction thereof. As the roller floor, i.e.,the support provided by rollers 100, width increases, the strength ofthe rollers must increase to avoid unacceptable deflection caused by thelonger roller length. Increased strength requires increased weight andrequires larger diameter rollers 100 as flooring for layer head 22. Bothaspects negatively and inefficiently affect machine performance whenroller length exceeds item 18 layer dimensions. In accordance with thepresent invention, however, rollers 100 are of minimal length justsufficient to support a tightly-organized item 18 layer thereon.

[0043] Thus, a synchronized palletizer has been shown and described. Thesynchronized palletizer provides a compact overall size with high itemthroughput. Most low infeed, i.e., production level infeed, palletizersrequire a pallet position, a layer build position, and a row buildconveyor. The layer build position is essentially eliminated by buildinglayers on the layer head 22 which also serves also as a layer placementmechanism, i.e., placing item 18 layers on a pallet 40 or stack of item18 layers. This feature is believed to save approximately 25% to 35% ofotherwise required floor space. The synchronized palletizer utilizes arelatively high speed row conveyor to chase down a current position ofthe layer head 22. Generally, conventional layer building brings eachrow to a fixed and maximum height, i.e., above any potential height fora stack of item 18 layers, for each and every row. Each row need only beraised to the height of the current stack level, i.e., to where layerhead 22 is positioned just above pallet 40 or a stack of item 18 layersresting on pallet 40. In this manner, the synchronized palletizerreduces travel distance and travel time for items conveyed to a layerbuilding site.

[0044] While illustrated as having two side plates 109, one at each endof rollers 100, the synchronized palletizer may be operated with onlyone side plate 109. The presence of a support area beyond rollers 100and adjacent thereto facilitates loose packing of item 18 rows duringconstruction of an item 18 layer on layer head 22.

[0045] As discussed above, dead plate 108 provides both a compressionfunction and a guiding function. With respect to compression, dead plate108 engages an item 18 layer and brings together or compresses thelayer. With respect to its guiding function, dead plate 108 maintainscontact with the first-to-drop row of items 18 thereby preventingtipping of the items as the rollers 100 move out from underneath. Asdiscussed hereafter, a back clamp assembly 210 also provides the dualfunctions of compression and guiding during release of items from alayer head.

[0046]FIG. 6 separately illustrates back clamp assembly 210 according toan embodiment of the present invention. In FIG. 6, back clamp assembly210 includes a left drive 212 a, a right drive 212 b, and a back clampbar 214. Each of left drive 212 a and right drive 212 b couples to clampbar 214 for reciprocating movement thereof. A synchronizing drive shaft215 also couples together left drive 212 a and right drive 212 b forcoordinated movement thereof. Generally, drives 212 a and 212 b pullclamp bar 214 up from a submerged position, across an item layerbuilding area, and return clamp bar 214 to the submerged position. Aleft side plate 216 a and right side plate 216 b in FIG. 6 arecoincident with a layer building surface 217 supporting a layer 282 ofitems 284 resting on a layer head 280. Drives 212 a and 212 b bringclamp bar 214 from below side plates 216 a and 216 b upward and toward alayer 282 of items 284 as described more fully hereafter. For thepresent discussion, it will be understood that drives 212 a and 212 beach mount upon layer head 280 and side plates 216 a and 216 b form aportion of the layer building surface 217 provided by layer head 280(FIGS. 7-10).

[0047] Layer head 280 corresponds generally to layer head 22 asdescribed above. Layer head 280, however, includes back clamp assembly210 as described hereafter in place of dead plate 108. Back clampassembly 210 provides the dual functions of compression and guiding asdescribed above with respect to that provided by dead plate 108.Accordingly, layer head 280 will not be described in full detail, itbeing understood that layer head 280 is generally similar to layer head22 in its structure and operation, with the exception that layer head280 includes back clamp assembly 210 in place of dead plate 108.

[0048] Thus, layer head 280 operates within the context of a palletizingoperation wherein successive layers 282 are constructed upon layer head280 and deposited upon a pallet or stack of layers 282 therebelow. Inother words, layers 282 are constructed upon layer head 280 and aredropped through a retractable floor of layer head 280 for deposit upon apallet or stack of layers therebelow.

[0049] Left drive 212 a includes a double-ended pneumatic cylinder 220a. Left drive 212 a includes a forward pulley 222 a and a rearwardpulley 224 a. A forward coupler 226 a of pneumatic cylinder 220 acouples to a first end of cable 230 a. A rearward coupler 228 a ties tothe other end of cable 230 a. Cable 230 a routes from coupler 226 aaround pulley 222 a and rearward around pulley 224 a to its connectionwith coupler 228 a. In FIG. 6, coupler 228 a is shown in both itsretracted and extended positions while coupler 226 a is shown only inits retracted position. It will be understood, however, that duringoperation of pneumatic cylinder 220 a couplers 226 a and 228 a remain afixed distance apart while reciprocally moving cable 230 a.

[0050] Right drive 212 b includes a similar arrangement. Moreparticularly, right drive 212 b includes a pneumatic cylinder 220 b withcouplers 226 b and 228 b each tied to respective ends of a cable 230 b.Cable 230 b engages pulleys 222 b and 224 b.

[0051] With respect to cables 230 a and 230 b, while illustratedschematically herein as cables it will be understood that a variety ofdevices may be employed to move clamp bar 214. For example, drive belts,chains, and other such devices may be used in conjunction with pulleys222 a, 222 b, 224 a, and 224 b to carry clamp bar 214 along the pathdescribed and illustrated herein. In addition to pulleys and suchdevices as drive belts, chains, and the like, it will be understood thata variety of mechanical architectures may be employed to move a clampbar from a submerged position into an operating position as describedherein. Accordingly, the present invention and any embodiments thereofwill not be limited to the specific cable illustrated and describedherein but will be taken to include other such devices capable ofcarrying clamp bar 214 as described herein.

[0052] Thus, when operated in unison pneumatic cylinders 220 a and 220 breciprocate cables 230 a and 230 b together through forward and rearwardmotion. Synchronizing drive shaft 215 ties together pulleys 222 a and222 b and thereby unifies movement of cables 230 a and 230 b. In otherwords, by virtue of synchronizing drive shaft 215 clamp bar 214maintains a given orientation within lift head 280. More particularly,clamp bar 214 remains parallel to the front and rear edges of layer head280. Clamp bar 214 couples to cables 230 a and 230 b. Thus, clamp bar214 follows cables 230 a and 230 b. With this arrangement, clamp bar 214may be positioned below side plates 216 a and 216 b as illustrated inFIG. 6. Activating pneumatic cylinders 220 a and 220 b moves cables 230a and 230 b rearward, i.e., from pulleys 222 a and 222 b toward pulleys224 a and 224 b. This causes back clamp bar 214 to move initially androtationally along the periphery of pulleys 222 a and 222 b andthereafter linearly rearward toward pulleys 224 a and 224 b. As aresult, back clamp bar 214 first resides below side plates 216 a and 216b, but may be brought up and out of this submerged position and to movelinearly and parallel to, but above, side plates 216 a and 216 b.

[0053]FIGS. 7 and 8 illustrate back clamp assembly 210 as integratedinto lift head 280. Portions of lift head 280 in the vicinity of rightdrive 212 b are omitted to better show portions of back clamp assembly210. In FIG. 7, drives 212 a and 212 b have been activated, i.e.,pneumatic cylinders 220 a and 220 b driven rearward, to position clampbar 214 most forward and in its submerged position below side plates 216a and 216 b (side plate 216 b being omitted from FIG. 7). FIG. 8illustrates back clamp assembly 210 with pneumatic cylinders 220 a and220 b driven forward to bring clamp bar 214 up from its submergedposition and forward along side plates 216 a and 216 b (side plate 216 bbeing omitted from FIG. 8). FIGS. 7 and 8 also illustrate a layer 282 ofindividual items 284. Layer 282 may be constructed or formed upon layerhead 280 by pushing or pulling rows of items 284 onto layer head 280. InFIG. 7, with clamp bar 214 in its submerged position below side plates216 a and 216 b, items 284 may be pulled or pushed onto layer head 280directly over clamp bar 214. In other words, bar 214 does not obstructpassage of items 284 thereover. Once a layer has been formed on layerhead 280, back clamp assembly 210 may be activated and brought to theposition illustrated in FIG. 8 and thereby engage item layer 282.

[0054]FIG. 9 illustrates layer head 280 with a layer 282 thereon. In theview of FIG. 9, most of back clamp assembly 210 is obscured, however,clamp bar 214 may be seen in its submerged position below side plates216 a and 216 b. Layer 282 has been brought onto layer head 280 by, forexample, pushing or pulling items 284 onto a roller floor 285 and sideplates 216 a and 216 b. As described more fully hereafter, roller floor285 retracts from below layer 282 and thereby drops layer 282 throughlayer head 280 for deposit therebelow upon a pallet or stack of layers282.

[0055] After a complete layer 282 has been formed upon layer head 280,left side clamp 286 a and right side clamp 286 b are activated tolaterally collapse layer 280, i.e., push layer 280 off of side plates216 a and 216 b and inward wholly onto roller floor 285. Each of sideclamps 286 a and 286 b include a clamp bar 288 a and 288 b,respectively. In the particular embodiment illustrated herein, clampbars 288 a and 288 b extend laterally inward and toward one another bymeans of scissor bars 290 a and 290 b, respectively. Each bar 288 a and288 b is supported at each end thereof by a block 292. The lower edge ofeach bar 288 a and 288 b is thereby spaced vertically above roller floor285 and above side plates 216 a and 216 b sufficient distance to allowpassage of clamp bar 214 therebetween. In other words, bars 288 a and288 b operate sufficiently above side plate 216 a and 216 b and rollerfloor 285 whereby clamp bar 214 may be brought out of its submergedposition and into engagement with layer 282 without interference fromside clamps 286 a and 286 b. In some embodiments, clamp bar 214 canslide directly upon the upward-facing surface of side plates 216 a and216 b. Accordingly, operation of clamp bar 214 and operation of sideclamps 286 a and 286 b can occur without interference therebetween.

[0056] In FIG. 10, clamp bar 214 has been brought out of its submergedposition and into engagement with layer 282 while side clamps 286 a and286 b are extended laterally inward without interference therebetween.In this respect, clamp bar 214 serves its compression function byoperating in conjunction with side clamps 286 a and 286 b and with stop211 to compress together laterally and longitudinally inward the items84 to form a well organized layer 282.

[0057]FIGS. 11-16 illustrated schematically the operation of layer head280 including clamp bar 214 as described herein. In FIG. 11, a firstlayer 282 a resides directly below layer head 280. In other words,earlier palletizing operations formed and deposited layer 282 a uponanother layer 282 or a pallet (not shown). Layer head 280 is thenpositioned just above layer 282 a to form a next layer 282 b of items284. The roller floor 285 together with side plates 216 define the layerbuilding surface 217. Clamp bar 214 resides below layer building surface217 and items 284 are pushed or pulled onto surface 217, as indicated atreference numeral 300.

[0058] In FIG. 12, a complete layer 282b has now been formed upon layerbuilding surface 217. This formation process includes laterally inwardcompression by means of side clamps 286 a and 286 b (not illustrated inFIGS. 11-16) and longitudinal compression by means of layer 282 bcaptured between clamp bar 214 and stop 211. Thus, as illustrated inFIG. 12 back clamp assembly 210 has been activated to bring clamp bar214 out of its submerged position below surface 217 and toward stop 211.With layer 282 captured between bar 214 and stop 211, layer 282 islongitudinally compressed.

[0059] In FIG. 13, roller floor 285 begins to move out from under layer282 b. The first-to-drop row 284 a remains in contact with clamp bar214. Without such contact, the first-to-drop row 284 a can tip off ofthe trailing member of roller floor 285 and tip out of the desired layerpattern. In other words, the first-to-drop row 284 a can fall out ofposition as it comes to rest on the layer 282 a therebelow. With clampbar 214 positioned as illustrated in FIG. 13, however, such displacementdoes not occur.

[0060] In FIG. 14, the first-to-drop row 284 a has fallen through layerhead 280 and onto layer 282 a therebelow. Roller floor 285 continues tomove out from under layer 282 c as each successive next-to-drop row ofitems 284 falls through the opening left behind roller floor 285. Eachsuccessive row of items 284 maintains its position by virtue of contactwith the previously dropped row and the next-to-drop row of items 284 a.In other words, each row of items 284 enjoys guiding support as it fallsfrom layer head 280. The first-to-drop row 284 a enjoys support fromclamp bar 214. The last-to-drop row 284 b enjoys support from thepreviously dropped row of items 284 and stop 211. Intervening rows,i.e., rows between the first-to-drop row 284 a and the last-to-drop row284 b enjoy guiding support from surrounding rows of items 284. As aresult, each row of items 284 falling from layer head 280 as rollerfloor 285 moves out from thereunder enjoys guiding support and therebyarrives in a desired position upon a layer of items 284 therebelow orupon a pallet therebelow.

[0061]FIG. 15 illustrates complete deposit of layer 282 b upon layer 282a. In other words, roller floor 285 has moved completely out from itssupporting position relative to layer 282 b and layer 282 b has fallenthrough the opening left by roller floor 285. Once a layer has been sodeposited, layer head 280 can be repositioned to receive a next layer282.

[0062] In FIG. 16, layer head 280 has been moved upward and slightlyabove layer 282 b. Roller floor 285 has been returned to its closedposition coincident with side plates 216 a and 216 b and layer buildingsurface 217, and clamp bar 214 has been returned to its submergedposition below surface 217. Accordingly, layer head 280 is now ready toreceive additional items 284 to form a next layer 282 of items 284 uponsurface 217. Eventually, a sufficient number of layers 282 have beenstacked below layer head 280 and the stack of layers 282 may be removed.

[0063] It will be appreciated that the present invention is notrestricted to the particular embodiment that has been described andillustrated, and that variations may be made therein without departingfrom the scope of the invention as found in the appended claims andequivalents thereof.

What is claimed is:
 1. In a palletizing device including a layerformation structure defining a layer building plane, an improvementcomprising: a contact element movable between a first position an asecond position, said first position being at least one of at and belowsaid layer building plane and said second position being above saidlayer building plane.
 2. An improvement according to claim 1 whereinsaid layer building plane lies coincident with a set of retractablerollers.
 3. An improvement according to claim 1 wherein said improvementfurther comprises: first and second actuators; and first and secondcables, said first cable being coupled to said first actuator and saidsecond cable being coupled to said second actuator, said contact elementcoupling said first and second cables, said first and second cablesmoving along a path including a path portion at or below said layerbuilding plane and a path portion above said layer building plane.
 4. Animprovement according to claim 1 wherein said improvement furthercomprises a plate as said contact element, said plate being pivotablebetween said first position and said second position.
 5. An improvementaccording to claim 1 wherein said improvement comprises said contactelement being moveable by at least one of linear and rotatable motionfrom said first position to said second position.
 6. An improvementaccording to claim 5 wherein said contact element mounts upon a flexiblesupport element and said flexible support element moves along a pathincluding portions adjacent to said first position and adjacent to saidsecond position.
 7. An improvement according to claim 1 wherein saidcontact element moves linearly into said second position.
 8. Apalletizing layer head comprising: a retractable floor movable between aclosed position coincident with a layer building plane and an openposition; and a contact element positionable between a submergedposition at or below said layer building plane and an engagementposition above said layer building plane.
 9. A palletizing layer headaccording to claim 8 further comprising side clamps.
 10. A palletizinglayer head according to claim 9 wherein said side clamps aresufficiently spaced relative to said layer building plane to allowmovement of said contact element between said layer building plane andsaid side clamps.
 11. In a method of constructing a stack of itemsincluding forming a layer of items upon a layer head and withdrawing afloor from thereunder, an improvement comprising: engaging afirst-to-drop set of items with a guide element as said retractablefloor moves out from under said first-to-drop set of items.
 12. A methodaccording to claim 11 wherein said engaging step includes moving saidguide element pivotally into contact with said first-to-drop set ofitems.
 13. A method according to claim 11 wherein said engaging stepcomprises moving said guide element linearly into contact with saidfirst-to-drop set of items.
 14. A method according to claim 11 whereinengaging step comprises guiding said first-to-drop set of items betweensaid guide element and a next-to-drop set of item.